1408 JOURNAL OF LIGHTWAVE TECHNOLOGY, VOL. 27, NO. 10, MAY 15, 2009

Experimental Comparison of TransmissionPerformance of Multichannel OFDM-UWB

Signals on FTTH NetworksMaria Morant, Student Member, IEEE, Tiago Ferreira Alves, Roberto Llorente, Member, IEEE,

Adolfo V. T. Cartaxo, Senior Member, IEEE, and Javier Marti, Member, IEEE

Abstract—The experimental demonstration of radio-over-fiberWimedia-defined OFDM ultrawide band (OFDM-UWB) wirelesstransmission in fiber-to-the-home (FTTH) networks using stan-dard single-mode fiber with lengths ranging from 25 to 100 km isreported in this paper.

The transmission performance of two multichannel UWB con-figurations, comprising three and five OFDM channels with QPSKand BPSK modulation per carrier respectively, is evaluated. Bothconfigurations transmit 1.56 Gbit/s aggregated bit rate, suitablefor integrated optical and wireless high definition video distribu-tion in FTTH networks. The experimental results show that an in-creased transmission reach can be achieved if the lower number ofOFDM-UWB channels at higher bit rate per channel configurationis employed.

Index Terms—Fiber-to-the-home (FTTH) access networks, or-thogonal frequency division multiplexing (OFDM), radio over fiber(RoF), Ultra-wide band (UWB).

I. INTRODUCTION

U LTRAWIDE band (UWB) wireless technology is experi-encing a fast market introduction targeting low-cost short-

range high bit rate cabling replacement for high-definition tele-vision (HDTV) audio/video. A large number of HDTV audio/video wireless solutions based on UWB technology have ap-peared in the market very recently [1]. Moreover, consumerUWB-enabled HDTV receivers, like [2], are being introducedin the market, which reveals UWB as the technology of choicefor low-cost wireless HDTV connectivity.

Fiber-based access, also known as fiber-to-the home (FTTH)networks, is also at deployment stage nowadays [3]. The

Manuscript received February 04, 2008; revised May 26, 2008 and July 31,2008. Current version published May 11, 2009. This work was supported in partby the FP7-ICT-216785 UCELLS and FP6-IST-33615 UROOF projects, and inpart by the e-Photon ONe+ NoE. The work of M. Morant was supported in partby Spain FPU MEC Grant AP2007-01413. The work of T. Alves work wassupported in part by the Fundação para a Ciência e a Tecnologia, from Portugal,under contract SFRH/BD/29871/2006.

M. Morant, R. Llorente, and J. Marti are with the Wireless-Photonics Inte-gration Group, Nanophotonics Technology Centre, Universidad Politécnica deValencia, Valencia 46022, Spain (e-mail: mmorant@ntc.upv.es; rllorent@ntc.upv.es; jmarti@ntc.upv.es).

T. F. Alves and A. V. T. Cartaxo are with the Optical Communications Groupof Instituto de Telecomunicações, DEEC, Instituto Superior Técnico, Lisboa1049-001, Portugal (e-mail: tiago.alves@lx.it.pt; adolfo.cartaxo@lx.it.pt)

Color versions of one or more of the figures in this paper are available onlineat http://ieeexplore.ieee.org.

Digital Object Identifier 10.1109/JLT.2008.2005252

availability of UWB wireless connectivity in HDTV equipmentopens up a window of opportunity for the cost-effective provi-sion of integrated UWB signals through FTTH networks.

UWB distribution on fiber is a natural step forward in accessnetworks. UWB is a radio modulation technique with 500 MHzminimum bandwidth or at least 20% greater than the centre fre-quency of operation [4]–[6], with a maximum transmission ca-pacity of 1.067 Gbit/s at 1.1 meters [7]. Interference with otherwireless services is mitigated transmitting at the level of para-sitic emissions in a typical indoor environment (FCC part 15:

41.3 dBm/MHz) [4]. The UWB-on-fiber approach exhibitsseveral advantages over other radio-over-fiber (RoF) solutions:1) The huge bandwidth of the fiber infrastructure can supportthe distribution of a large number of UWB wireless channelsin a frequency division arrangement. 2) UWB transmission iswell suited for the compensation of the fiber transmission im-pairments, namely chromatic dispersion, intrachannel nonlineareffects, and nonlinear phase noise [8] if Wimedia-defined or-thogonal frequency-division multiplexing (OFDM) modulationis employed [9]. 3) UWB-on-fiber is a low-cost approach. Byexample, the European project IST-UROOF develops an op-tical UWB receiver with a target cost under $100 [10]. 4) FTTHnetworks are transparent to the specific implementation em-ployed. This flexibility is of special interest for operators asUWB regulation is still evolving.

The UWB-on-fiber approach exhibits the advantage overbaseband distribution of UWB signals that, at reception,the signal is photodetected, amplified and directly radiated(without re-modulation or up-conversion stages). The simul-taneous transmission of a HDTV baseband signal altogetherup-converted UWB radio [11], [12] is not considered in thisapproach. This simplifies the overall distribution system andreduces the deployment cost as only standard low-cost UWBreceivers are required at subscriber premises. This approachcan be extended to 60 GHz UWB technology which is undermajor attention for broadband communications [13].

In this paper, the system-level balance between the numberof UWB channels and their modulation format, i.e., their per-carrier constellation order, in a multichannel UWB distributionsystem on FTTH is investigated.

The multichannel UWB signal is a Wimedia-definedOFDM-UWB signal as specified in the ECMA-368 standard[14], which can be allocated in the UWB band (3.1 to 10.6 GHz)[4]. OFDM-UWB is preferred over other UWB implementa-tion like impulse-radio (IR) UWB [11], or proprietary UWB

0733-8724/$25.00 © 2009 IEEE

MORANT et al.: TRANSMISSION PERFORMANCE OF MULTICHANNEL OFDM-UWB SIGNALS 1409

Fig. 1. (a) FTTH distribution of OFDM-based UWB signals (ECMA-368 stan-dard). (b) Diagram of the band group allocation in ECMA-368 [14].

solutions [14] due to the large market availability of low-costOFDM-based UWB solutions, which largely surpassed theother implementations.

Two different OFDM-UWB multichannel configurations arecompared. First, a three-channel quadrature-phase shift keyingOFDM (QPSK-OFDM) configuration is implemented and itstransmission performance is evaluated. Second, a five-channelbinary-phase shift keying OFDM (BPSK-OFDM) configura-tion is also implemented and its performance is evaluated. Bothconfigurations transport a 1.56 Gbit/s aggregated bitrate signal.Their performance is compared to identify the best performingsystem-level implementation.

This paper is structured in five sections. Section II describesthe UWB-on-fiber for FTTH networks approach, including thespecific UWB-OFDM configurations employed. Section IIIpresents the experimental setup and the two transmitter con-figurations implemented: first, a 3-channel QPSK-OFDMconfiguration, and second, a 5-channel BPSK-OFDM trans-mitter configuration. In Section IV, the experimental results aredescribed and discussed. Finally, the main conclusions of theexperimental work are presented in Section V.

II. OFDM-UWB DISTRIBUTION IN FTTH NETWORKS

The UWB-on-fiber distribution in FTTH networks approachis depicted in Fig. 1(a). This figure shows an optical line terminal(OLT) which distributes HD audio/video content from the corenetwork to a number of users through a FTTH network. TheOLT generates OFDM-UWB signals as defined by ECMA-368[14]. These signals are transmitted to the subscriber premises,where are received by a wireless extractor (UWE) system. TheUWE extracts the UWB signal from the FTTH fiber and trans-mits the UWB wireless signal to an UWB-enabled TV set [2]or computer [16]. The UWE performs the photodetection of thetransmitted signal, electrical filtering and amplification and di-rectly radiates the resulting signal to establish a standard UWBcommunication.

The UWB-on-fiber radio spectral mask is allocated between3.1 and 10.6 GHz, providing 14 channels with 528 MHz band-width, as shown in Fig. 1(b) [14]. The electrical UWB signal is

Fig. 2. FTTH architectures for a) configuration A (fiber path without opticalamplification) [18], and b) configuration B (fiber paths with inline optical am-plification) [19].

distributed through the FTTH network in a single wavelengthand broadcasted in the user premises. Multicast or unicast op-eration is possible increasing the number of UWB channelsavailable. This can be done employing different wavelengthsin a wavelength-division multiplexing (WDM) configuration.Nevertheless, the analysis of such configuration is out of thescope of this paper.

Each OFDM-UWB channel consists in 128 subcarrierscomprised by null subcarriers (specified at the band edges inorder to relax electrical filter requirements), pilot subcarriers,guard subcarriers, and data subcarriers. The OFDM symbolperiod is 312.5 ns and the data is transmitted in 242.42 ns. Theguard-time is 70.1 ns which comprises 60.61 ns for the cyclicprefix [17]. The subcarrier frequency spacing is 4.125 MHzand the total OFDM-UWB signal bandwidth is 528 MHz (128

4.125 MHz).Two FTTH configurations have been studied in this

experiment. The first one is labeled “FTTH configurationA” in Fig. 2(a) and consists in a conventional passive opticalnetwork (PON) architecture with a ‘trunk’ link connecting theOLT with the UWE at the subscriber base [18]. The second islabeled “FTTH configuration B” and is depicted in Fig. 2(b).This configuration simulates a FTTH link with intermediateoptical amplification, comprising a ‘trunk’ link that connectsthe OLT with the remote node and an ‘access’ link to reachthe UWE at subscriber premises [19]. Configuration B is com-monly used to provide triple play services with the addition ofcarriers incorporating local or regional programming and alsovoice and data services.

The fiber link distance in the direct connection case shown inFig. 2(a) can range up to 60 km. The long ‘trunk’ links shown inFig. 2(b) interconnect distribution hubs (DH) towns which canbe up to 100 km apart. The ‘access’ links shown in Fig. 2(b) con-nect the DH to the final subscriber, which can be up to 60 kmapart. These FTTH configurations are emulated in the experi-mental work by four transmission paths as described in the nextsection.

1410 JOURNAL OF LIGHTWAVE TECHNOLOGY, VOL. 27, NO. 10, MAY 15, 2009

Fig. 3. Experimental setup for OFDM-UWB transmission over four differentFTTH paths:���� �� � � �, ������ � � �,����� � � � and������ � ��� �.

III. EXPERIMENTAL ANALYSIS

In this section, the performance of two OFDM-UWB mul-tichannel transmission in four FTTH paths emulating the twoFTTH configurations depicted in Fig. 2 are analyzed experi-mentally. The target of the analysis is two fold: first, to demon-strate the feasibility of multichannel OFDM-UWB on FTTHnetworks at 1.56 Gbit/s aggregated bitrate—adequate for HDuncompressed video trans-mission [20]; second, to investigate the tradeoff between thenumber of channels and their modulation index at system level.The performance of the OFDM signal is evaluated at the sub-scriber stage, i.e., at point (1) in Fig. 1.

A. FTTH Demonstrator setup

The experimental analysis setup is shown in Fig. 3. Two dif-ferent OFDM-UWB transmitters are implemented: (A) A three-channel QPSK-OFDM UWB, and (B) a five-channel BPSK-OFDM UWB configuration. The bandwidth of each channel is528 MHz. These two configurations are implemented by an Ag-ilent 6030 arbitrary waveform generator (AWG) with 1.25 GS/ssampling rate and 15 bits vertical resolution per channel. TheOFDM-UWB signals are generated at baseband and up-con-verted to the 6.5 GHz central frequency for analysis. The base-band OFDM signal was generated offline in advance and sentto the AWG. Two output channels are available in AWG6030,which will be further employed to generate uncorrelated sidechannels.

The signal generated by the OFDM-UWB transmitter blockmodulates externally a continuous-wave 1555 nm laser usinga Mach–Zehnder electro-optical modulator (MZ-EOM) with20 GHz bandwidth (BW) at quadrature-bias (QB) point. Theaverage power in optical domain after modulation and beforetransmission, point (1) in Fig. 3, is set to 2 dBm to ensurelinear transmission into the optical link.

The resulting optical signal is then transmitted through thefour FTTH paths shown in Fig. 3, composed by different SSMFlengths ranging from 25 km to 100 km, corresponding to con-ventional FTTH transmission paths [21]. Optical amplificationusing erbium doped fiber amplifiers (EDFA) is used when nec-essary. After back-to-back configuration, the first analyzed path(Path #1) has 25 km of SSMF, simulating FTTH configuration

A described in Fig. 2(a). The second path (Path #2), with 50 kmreach, is obtained using two fiber sections with 25 km of lengtheach, with an EDFA between them. The third path (Path #3) with75 km of reach is composed by two fiber sections with length of50 km and 25 km and an EDFA between them. The last studiedpath (Path #4) has a reach of 100 km, and is composed by twofiber sections of 50 km with an EDFA between them. Paths #2,#3 and #4 simulate a FTTH link using configuration B describedin Fig. 2(b). The optical amplification is done by a 23 dB gain,4 dB noise figure EDFA (Keopsys KPS). The receiver includesa 4.5 dB noise figure, 19 dBm saturation power EDFA (ExeliteXLT) used for adjusting the received optical power level mea-sured at point (2) in Fig. 3.

After transmission, the signals are filtered by a 0.8 nm @0.5 dB optical filter and photodetected by a PIN photodiode

(0.65 A/W responsivity, 50 GHz bandwidth). In order toevaluate the performance of the UWB channel under study,the photodetected signal is down-converted to baseband andsampled by an HP83486A module (20 GHz bandwidth). Oncesampled, the channel under study is equalized from the pilotsubcarriers information, demodulated and the error-vectormagnitude (EVM) is evaluated directly from the receivedconstellation. The maximum permissible relative constellationerror is set to a root mean square (RMS) EVM of 14.13% [14].

B. Three-Channel QPSK-OFDM UWB Configuration

Fig. 4 shows the experimental setup for the 3-channelQSPK-OFDM UWB transmitter. The transmitter generatesa three-channel OFDM configuration comprising 128 car-riers per channel, including pilots. In this configuration, the128 subcarriers distribution is as follows: 82 informationsubcarriers, 42 pilot subcarriers and 4 null subcarriers. Eachsubcarrier is modulated in QPSK with an aggregated bit rateof 1.5689 Gbit/s. The three channels form a subcarrier mul-tiplexed (SCM) signal. The central channel—labeled CH2 inFigs. 4 and 5—is located at and used forperformance evaluation. This channel is surrounded by twoadjacent channels centered at frequencies and

respectively. The SCM signal bandwidth (SCMBW) is 3.5 GHz at 10 dB for the QPSK-OFDM-UWB SCMgroup. Two QPSK-OFDM-UWB channels are generated by theAWG and the third one is obtained from one of these ones afterdelay line decorrelation and electrical losses compensation(due to the power divider and the electrical time delay).

Fig. 5 shows the transmitted electrical spectrum measured forthe three-channel QPSK configuration at MZ-EOM input.

C. Five-Channel BPSK-OFDM UWB Configuration

Fig. 6 shows the transmitter of the five-channel BPSK-OFDM-UWB configuration. In this case, each UWB channelhas 128 subcarriers distributed in 98 information subcar-riers, 26 pilots subcarriers, and 4 null subcarriers. Eachsubcarrier is modulated by BPSK with an aggregated bit rate of1.5625 Gbit/s. The central channel is located atand is used for performance assessment. Neighboring channelsare centered at frequencies 4, 5.25, 7.75, and 9 GHz, usingtwo up-conversion processes with initial mixer frequencies of

MORANT et al.: TRANSMISSION PERFORMANCE OF MULTICHANNEL OFDM-UWB SIGNALS 1411

Fig. 4. Experimental setup of the 3-channel QPSK-OFDM-UWB transmitter.The center channel is centered at � � ��� ��� and is surrounded by twoadjacent channels centered at frequencies � � � ��� and � � � ���.

Fig. 5. Electrical spectrum for the 3-channel QPSK-OFDM configuration.

Fig. 6. Experimental setup of the five-channel BPSK-OFDM-UWB transmitterwhere the center channel is centered at � � ������. Using mixer frequen-cies � � �� ��� and � � �� ���, neighboring channels centeredat frequencies 4 GHz, 5.25 GHz, 7.75 GHz and 9 GHz are obtained.

and and then, the resultingsignal is up-converted to 6.5 GHz.

The transmitted signal spectrum at MZ-EOM input for thefive-channel BPSK-OFDM-UWB configuration is shown inFig. 7. In Figs. 5 and 7, the electrical spectrum distortion is dueto the frequency limitations of the electrical devices.

Fig. 7. Electrical spectrum for the 5-channel BPSK-OFDM configuration.

D. Receiver Processing

The received signal is down-converted to baseband and alow-pass filter ( 3 dB bandwidth of 1 GHz) is used to selectthe channel under study (channel located at 6.5 GHz). Thissignal is re-sampled and equalized from pilot compensation.This is possible due to the insertion of the pilot subcarriers inthe OFDM-UWB signal. These dedicated subcarriers transmitknown pilot symbols to assist the phase estimation, whereasthe remaining subcarriers transmit information symbols.

Pilot compensation is performed on the received signal usingthe information from the known module and phase of the in-serted pilots to estimate the module and phase error inducedby the transmission channel. After, the compensation of theseerrors along the channel bandwidth is accomplished using theperformed pilot-based estimation. The estimation is achieved byleast squares adjustment.

The RoF link performance is analyzed from the evaluationof the EVM of the received baseband OFDM signal, as it isshown in Fig. 3. The EVM root mean square (RMS) is computeddirectly from the demodulated constellation using [22]

(1)

where is the normalized symbol in the stream of mea-sured symbols, is the ideal normalized constellation pointof the symbol and is the number of transmitted symbols.The bit error ratio could be calculated, if desired, from the EVMmeasurements shown, as described in [22].

IV. PERFORMANCE MEASUREMENTS

Two sets of measurements have been done on four FTTHSSMF transmission paths depicted before in Fig. 3, and for dif-ferent optical received power levels measured at point (2) inFig. 3. Fig. 8(a) and (b) show the corresponding received con-stellations after fiber transmission along Path #3 (75 km lengthwith amplification) with 6 dBm of received optical power level

1412 JOURNAL OF LIGHTWAVE TECHNOLOGY, VOL. 27, NO. 10, MAY 15, 2009

Fig. 8. (a) Received BPSK constellation, (b) received QPSK constellation(both for 6 dBm received optical power after 75 km fiber transmission (Path#3)),and the resulting constellations after equalization for (c) BPSK and (d) QPSK.

Fig. 9. EVM experimental results: three channels QPSK-OFDM in back toback configuration, and after 25 km, 50 km, 75 km and 100 km transmissionthrough SSMF. Dashed line indicates the EVM threshold for UWB communi-cation.

for BPSK and QPSK, respectively, and Fig. 8(c) and (d) the re-sulting constellations after equalization using pilot tones infor-mation.

The experimental results of EVM for the 3-channel QPSKand 5-channel BPSK configurations are shown in Fig. 9 and 10,respectively. In each figure, the EVM results obtained for thefour FTTH paths shown in Fig. 3 are represented. The EVMthreshold for successful UWB communication of 14.13% [14]is shown as a dashed horizontal line in Figs. 9 and 10.

Comparing the EVM results in Figs. 9 and 10 for the fourFTTH paths, it can be observed that performance degradeswhen transmitting along longer optical transmission paths. Thedegradation is mainly due to the fiber dispersion-induced powerfading [23]. Additional degradation occurs because longerdistances lead to higher optical noise power originated by theoptical amplifiers described in Section III. Higher optical noisepower levels lead to EVM degradation.

Fig. 9 shows also that the EVM of the 3-channel QPSKconfiguration follows approximately a linear dependence of theEVM on the measured received optical power. However, for

Fig. 10. EVM experimental results: five channels BPSK-OFDM in back toback configuration and after 25 km, 50 km, 75 km and 100 km transmissionthrough SSMF. Dashed line indicates the EVM threshold for UWB communi-cation.

large optical powers, a significant saturation effect of the EVMdependence on the received optical power can be noticed. Infact, in the saturation zone, the EVM tends to stabilize, andits reduction with the increase of the received optical power isvery small.

The saturation behavior can be attributed to the dominanceof optical noise with respect to electrical noise at high opticalpower levels received at the PIN input. In case of dominance ofoptical noise, no performance improvement can be achieved byincreasing the received optical power at the PIN input throughthe optical pre-amplifier gain increase. Fig. 10 shows a similarlinear dependence for the EVM of the 5-channel BPSK config-uration and a stronger saturation effect. The saturation zone ismarked in grey in Figs. 9 and 10.

From the experimental results, it can be also seen that3-channel QSPK-OFDM UWB exhibits better performancethan the 5-channel BPSK-OFDM UWB configuration. This isdue to the multichannel effects, more intense in the five-channelconfiguration due to the higher number of channels and thesmaller channel spacing in the BPSK configuration.

V. CONCLUSION

In this paper, the transmission of two ECMA-368OFDM-UWB configurations through different FTTH fiberpaths has been reported. The two configurations consideredare three-channel QPSK-OFDM UWB, and five-channelBPSK-OFDM UWB. The experimental results demonstrate thefeasible distribution of OFDM-UWB at[14] with 100 km reach in a three-channels QPSK-OFDMUWB configuration, and with 25 km reach in a five-channelsBPSK-OFDM UWB configuration.

Two system-level configurations have been compared froma system point of view in order to provide a given bit rate toUWB-on-fiber final user. First, a lower number (3 channels)of channels bearing a higher-order constellation (e.g., QPSK)and, second, a larger number (5 channels) bearing a lower-orderconstellation (e.g., BPSK). The results show better performancefor the QPSK-OFDM configuration, which uses larger channelspacing and comprises a smaller number of channels occupying

MORANT et al.: TRANSMISSION PERFORMANCE OF MULTICHANNEL OFDM-UWB SIGNALS 1413

a smaller bandwidth. Nevertheless, other transmission schemescould give different results and further investigation would berequired in this case.

The better performance of the 3-channel QPSK-OFDM con-figuration compared with the 5-channel BPSK-OFDM indicatesthat multichannel effects can be very relevant in this technique.The optical transmission reach is limited by the chromatic dis-persion to around one hundred kilometer. Dispersion compen-sation would be required to exceed this distance.

Future work is required to derive the performance scalabilitywith the impairments identified and to evaluate the limits of theUWB-over-fiber technique. This would give clear guidance foroperators interested in deploying this technology.

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Maria Morant received the M.Sc. degree inTelecommunication Engineering in 2008 from theUniversidad Politécnica de Valencia, Spain. Sheis currently working towards the Ph.D degree inTelecommunications at wireless-photonics integra-tion NTC area.

Since 2006, she has been collaborating with theValencia Nanophotonics Technology Center (NTC)in ultra-wideband radio signals propagation overoptical fiber and is working in European projectsas FP6-IST-UROOF and FP7-ICT-UCELLS. Her

current research areas of interest include ultra wideband communications onfiber optic networks.

Tiago Ferreira Alves received the “Licenciatura”degree in electrical and computer engineering fromInstituto Superior Técnico (IST), UniversidadeTécnica de Lisboa, Portugal, in 2006. He is currentlyworking towards the Ph.D. degree in electrical andcomputer engineering at IST.

Along two years, he has contributed with morethan 15 papers to international conferences and jour-nals. He participated in the National (Portuguese)project SHOTS, in the field of high-speed WDMsystems, and in the European Project e-Photon one+.

He is also involved in the European project FIVER. His current areas of interestare wavelength division multiplexing systems, ultra-wideband radio-over-fibresystems, and photonic time-stretching systems.

Roberto Llorente received the M.Sc. degree intelecommunication engineering from the Poly-technic University of Valencia, Spain, in 1998. Sincethen, he has been in research positions within theFiber-Radio Systems Group of the same university.In 2002 he joined the Valencia NanophotonicsTechnology centre (NTC), where he has participatedin several national and European research projectson areas such as bio-photonics, optical signal pro-cessing and OTDM/DWDM transmission systemsworking toward the Ph.D. received in 2006.

Currently, he is Associate Professor of the Universidad Politécnica deValencia in the Communications Department, teaching radio-communicationsrelated subjects. He has been the Technical Responsible of the Europeanproject FP6-IST-UROOF in the NTC, and, from January 2008, Coordinator ofthe European project FP7-ICT-UCELLS. His reseach interest include opticaland electro-optical processing techniques in the areas of transmission systemsand hybrid wireless-optical access networks. He has authored or co-authoredmore than 40 papers in leading international journals and conferences and hasauthored three patents.

1414 JOURNAL OF LIGHTWAVE TECHNOLOGY, VOL. 27, NO. 10, MAY 15, 2009

Adolfo V. T. Cartaxo received the degree of "Licen-ciatura" in electrical and computer engineering, andthe Ph.D. in electrical and computer engineering in1985 and 1992, respectively, from Instituto SuperiorTécnico (IST), Lisboa, Portugal.

He is currently Associate Professor at the Elec-trical and Computer Engineering Department ofIST. He joined the Optical Communications Group(OCG) of IST as a Researcher in 1992, and he is nowthe leader of the OCG conducting research on opticalfiber telecommunication systems and networks. He

is leader of the IST participation in several national and international (of theEuropean Union programs on R&D) projects in the optical communicationsarea. He has acted often as a technical auditor and evaluator of R&D projects forvarious organizations. He has served as a reviewer for several top publicationsin the area of optical communications and networks. He is a senior memberof the IEEE Laser and Electro-Optics Society. He has authored more than 65refereed publications in technical journals, and more than 90 internationalconference papers. He is coauthor of two patents. His current research areas ofinterest include fiber optic communication systems and networks.

Javier Marti received the Ingeniero de Telecomu-nicación degree from the Universidad Politécnicade Catalunya, Spain, in 1991, and the Ph.D. degreefrom the Universidad Politécnica de Valencia, Spain,in 1994. During 1989 and 1990, he was an AssistantLecturer at the Universidad Politécnica de Catalunya.

Since 1991 to 2000, he obtained the positions ofLecturer and Associate Professor at the Telecom-munication Engineering Faculty, where he iscurrently a Full-Professor and leads the Fiber-RadioGroup. Nowadays he is the Director of the Valencia

Nanophotonics Technology Centre (NTC), a national research centre forphotonic technologies in Spain. He has authored 7 patents and over 185 papersin refereed international technical journals in the fields of fiber-radio systems,technologies and access networks. He has led many national and internationalresearch projects (FP5-IST-TOPRATE) and has been the coordinator ofthe FP5-IST-OBANET and FP6-IST-GANDALF projects. He is currentlyparticipating IST-LASAGNE and coordination FP6-IST&NMP-PHOLOGIC.

Prof. Martí is or has been a member of the Technical Program Committeeof several conferences such as ECOC, LEOS, Microwave Photonics, and sev-eral other international workshops. He is currently involved in launching NTCspin-off companies addressing photonic-wireless technologies. He is also therecipient of several academic and industrial awards in Spain.